Memantine blocks mitochondrial OPA1 and cytochrome c release and subsequent apoptotic cell death in glaucomatous retina.
OBJECTIVE
To determine whether intraocular pressure (IOP) elevation alters OPA1 expression and triggers OPA1 release, as well as whether the uncompetitive N-methyl-d-aspartate (NMDA) glutamate receptor antagonist memantine blocks OPA1 release and subsequent apoptotic cell death in glaucomatous DBA/2J mouse retina.


METHODS
Preglaucomatous DBA/2J mice received memantine (5 mg/kg, intraperitoneal injection, twice daily for 3 months) and IOP in the eyes was measured monthly. RGC loss was counted after FluoroGold labeling. OPA1, Dnm1, Bcl-2, and Bax mRNA were measured by qPCR. OPA1 protein was assessed by immunohistochemistry and Western blot. Apoptotic cell death was assessed by TUNEL staining.


RESULTS
Memantine treatment significantly increased RGC survival in glaucomatous DBA/2J mice and increased the 75-kDa OPA1 isoform, but did not alter the 80- and 90-kDa isoforms. The isoforms of OPA1 were significantly increased in the cytosol of the vehicle-treated glaucomatous retinas but were significantly decreased in memantine-treated glaucomatous retinas. OPA1 immunoreactivity was decreased in the photoreceptors of both vehicle- and memantine-treated glaucomatous retinas, but was increased in the outer plexiform layer of only the memantine-treated glaucomatous retinas. Memantine blocked apoptotic cell death in the GCL, increased Bcl-2 gene expression, and decreased Bax gene expression.


CONCLUSIONS
OPA1 release from mitochondria in glaucomatous mouse retina is inhibited by blockade of glutamate receptor activation. Because this OPA1 effect was accompanied by increased Bcl-2 expression, decreased Bax expression, and apoptosis blockade, glutamate receptor activation in the glaucomatous retina may involve a distinct mitochondria-mediated cell death pathway.
Ju
Won-Kyu
WK
Hamilton Glaucoma Center, University of California San Diego, La Jolla, California 92037, USA. danielju@glaucoma.ucsd.edu
Kim
Keun-Young
KY
Angert
Mila
M
Duong-Polk
Karen X
KX
Lindsey
James D
JD
Ellisman
Mark H
MH
Weinreb
Robert N
RN
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002470:Cell Survival; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism*; D034284:Dynamin I / Q000235:genetics; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005901:Glaucoma / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007274:Injections, Intraperitoneal; D007429:Intraocular Pressure; D008559:Memantine / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012164:Retinal Diseases / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D012165:Retinal Ganglion Cells / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000235:genetics
C494827:Bax protein, mouse; D018691:Excitatory Amino Acid Antagonists; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D034284:Dynamin I; D020558:GTP Phosphohydrolases; C498809:Opa1 protein, mouse; D008559:Memantine